Return bend



y 23, 1940- G. 'r.' JACOCKS 2,202,491

RETURN BEND Filed Oct. 9. 1957 5 Shegts-Sheet 1 Fi y. 1.

10 I [Z a I 18 Q [2 I F 2 v Fig. 3.

INVENTOR.

George Ja'cocks AT EY Q f 10 l I.

8, 1940- G. JACOCKS I 2,202,491

RETURN BEND Filed 001;. 9, 1937 s Sheets-Sheet 2 Fig. 4. [46' Z5 M [79.51 4 Fzg. 6. [4c

A INVENTbRV George TJaeock's AT EY May 28 1940.

INVENTOR.

6 ye Jacoeks W4? ATT EY Patented May 28, 1940 UNITED s'rATEs' PATENT OFFICE RETURN BEND George T. Jacocks, Larchmont, N. Y., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application October 9, 1937, Serial No. 168,139

8 Claims. (01. 285-20) a constant cross sectional area between the tube contacting surfaces, the sealing of the parts' being removed from the abutting surfaces to maintain the uniform internal cross section of the return bend and tubes and for protection of the m sealing device and to prevent erosion.

Another object of the invention is to provide an improved form of sealing gasket for a return bend which is sealed with respect to the tubes with an increasing tightness of the gasket as the 20 return bend comes into contact with the tube abutment, the gasket tension exceeding the total tension between the returnbend and the tubes,

and being independent thereof. p A still further object of the invention is to provide an improved connection between a tube sheet 4 and a return bend in which the parts are held together by adjustable means in compression with a .minimum of metal between the adjustable means and the gasket to reduce expansion and contraction of the parts under high temperature changes.

A more specific object of the invention is to provide a high pressure and high temperature return bend for interconnecting a plurality of tubes with a direct gasket relation with the tube walls,

, the tubes being provided with sleeves of alloy metal with which thegasket cooperates so that tube creep is reduced to a minimum and the seal is not reduced in efllciency.

" Further objects and advantages of my invention will appear from the following description'of preferred forms of embodiment thereof, taken in connection with the attached drawings illustrative thereof, and in which:

parts broken away and shown in section;

Fig. 2is an end elevation of the return .bend shown in Fig. 1 with parts cut away and shown no'in section;

Fig. 3 is a plan view of an abutment ring for securing the tubes to the tube sheet;

Fig. 4 is a top plan view of the return bend with parts broken away and shown in section; 65 Fig. '5 is a detailed cross section showing the Fig. l is a side elevation of a return bend with,

relation of the parts in a partially assembled potion; I

Fig. 6 is a view similar to Fig. with the parts in an assembled position;

Figs. 7 and 8 are detailed cross sectional views 5 similar to Fig. 5 but showing a modified form of construction in the partially assembled and fully assembled positions respectively; v

' Figs. 9 and 10 are detailed cross sectional views similar to Fig. 5 showing a still further modified 1 form of construction with the parts in a partial- 1y assembled and fully assembled position" respectively.

In accordance with one preferred form of embodiment of my invention, the return bend as- 1 sembly consists essentially of a tube sheet ill to which the tubes I2 are attached, and the return bend I 4 which has an internal channel l5 by which the tubes are rendered effectively continuous. In this form, the tube sheet I0 is provided with apertures l6 through which the tubes I2 extend, and shoulders I! on the tube sheet l0 surrounding the apertures l6, support the split ring l8 which in turn supports the upset shoulders l2a of the tubes l2. Such construction permits a ready attachment and removal of the tube sheet Ill from the tubes I2 as the ring may be removed as desired. It is to be understood, however, that the tubes may be expanded in the tube sheet by the methods commonly used but as will 3 hereinafter appear, such expansion is not necessary. p

The return bend I4 is preferably secured to the tube sheet III by means of screws 20, the screw threads of which engage in the screw threaded 86 parts of bosses 2| integrally formed as skirts or projections of the tube sheet I!) as will be apparent from the inspection of Fig. 4. This upstanding skirt or boss portion forms a recess into which the return bend it telescopically fits, the 40 return bend having a smooth bore I40 to serve as the screw abutment, complementary to the screw threaded portionli on the tube sheet. The threaded screw portion 25 in the bosses. 2| is approximately two-thirds of the diameter of the 5 screw, which is found to be adequate. The bottom of the. screws 20 engage a projecting foot or lug portion Mb on the return bend l4 and by using anenlarged contacting surface, a substantially reduced unit pressure on the screw is possible.

This form of screw is especially effective in heat transfer work for any tendency of the screw to expand under increases of temperature will tend to more securely seal the return bend to the tubes iii due to its compression action. It is to be noted, however, that the screws are spaced a substantial distance from the internal channel it, and thus away from the greatest heat. In addition the screw threaded portion of the screw is in engagement with the threaded portion 25 of the tube sheet, and as such portion is externally exposed, the screw has a relatively slight temperature change. l a

The tubes are sealed with respect to the return bend It in one preferred manner by a ring form of gasket 25, which is normally in the shape of an inverted frustrum of a cone. To accommodate this gasket, both the return bend it! and the ends of the tubes it are provided with shoulder portions shown in Fig. 5. The shoulder Ma on the return bend it has a rounded fillet with which one end of the gasket 26 contacts and the tube above the upset portion 92a has a shoulder lib with which the other end of the gasket contacts. The angular contact which the gasket makes with respect to the line of force applied by the screws 26, is preferably of a low order and the tube 52 with the surfaces E and Me of the respective elements in contact as shown in Fig. 5. It will be appreciated that the extent of the sealing pressure will depend on the angular change of the gasket and not on the relative movement of. the return bend with respect to .the'tube sheetor the pressure required to force the parts together. If the angle is initially great, the movement will cause a substantial seal as the change is the difference between the sine of the final angle and the sine of the initial angle.

If desired the abutting surfaces We and Me may be provided with shallow grooves 28, which will normally carbonize if high pressure hydrocarbons are conducted through the return bend and tubes. The gasket is spaced from the fluid path eliminating any erosion or corrosion and, as the internal channel it in the return bend it is of thesame cross sectional diameter as'the diameter of the tubes, there is no change of cross section in area or shape at any point in the fluid path. The interior of the return bend is truly streamlined and continuous between the surfaces abutting the tube ends and is thus free or eddy forming causes.

The gasket 2 3 may be made of any suitable metal, but it is preferably softer than the tubes or return bend, and it has such elasticity that even after long service it will tend to return to its initial shape. It may be reused as it is readily reformed to its initial condition; Its elasticity facilitates removing the return bend as it tends to open the joint when the screws are removed. ltis of course to be understood that other forms of gaskets can be used in lieu of the toggle form of gasket shown, and it is also obvious that other forms of securing means can be used in lieu of the compression screws. More effective heat transfer is accomplished by uniformity of cross section and absolute tightness of the joints, how

ever, and these objects are more effectively accomplished by the particular toggle form oi gas ket which has a sealing pressure in excess of. the longitudinal pressure holding the return bend to the tube sheet and the compression type of screws which retain the-seal regardless of temperature change.

The amount of metal in the lugs lflb-is conveniently of minimum thickness with the compression screws 26 and with the distance between the gasket 26 and the bottom of screw 20 low, there is very little metal to change under temperature variations. With repeated heating and cooling, there is 'no tendency to overstress the metal or develop leaks. These lugs Nb and the bosses 2!, also facilitate stacking of the tubes as staggered constructions are possible.

A modified form of construction is shown in Fig. '7 and Fig. 8, with the tubes til expanded into the tube sheet 32 as shown at 33.

As in the prior construction, the tubes 3d are sealed directly to the return bend it by the gasket 35 and the return bend as well as the tube ends is provided with shoulders for this purpose. It may be desirable, however, to use a collar or sleeve 36, on the shoulder 3011 on the tube and such collar or sleeve may be of a suitable alloy, as for example, one containing 445% of chromium and of molybdenum, which will prevent creep of the tube under high temperature and the pressure of the gasket. It is preferable that the sleeve or collar 36 be welded at 37 to the tube to retain it in place, but it is usually of such thin metal that it will be sealed by gasket pressure against the tube itself.

In Figs. 9 and 10, the tubes 40 are also expanded into the tube sheet 32 but in this construction the return bend 83 is sealed with respect to the tube sheet 42 rather than directly with the tubes as in the prior construction. Shoulders 3211 in the tube. sheet and 63a in the return bend it provide the diametrically opposite contact portions for the gasket 45. Application of longitudinal pressure between the return bend and tube sheet will cause a partial rotation of the gasket on an axis normal to a transverse plane through the gasket so that the lateral force at the diametrically opposite edges is increased to maintain the desired seal, and as the seal increases as the parts are brought t'ogather, the tubes and return bend can be brought into abutting relation to prevent any change of cross section from tube to tube and the tubes may be of uniform diameter throughout.

In these several forms of embodiment of the invention, it is desirable thatthe edges of the gasket be rounded and that the shoulders with which the gasket edges contact also be rounded, and to the same radius. The angular change of the gasket is thus of a rolling nature, and -not only facilitates the closing together of the parts, but maintains an effective seal irrespective of the angular position. Furthermore, the entire arc of contact assists in sealing under high pressures.

While I have shown preferred forms of embodiment of my invention, I am aware that other modifications may be made thereto, and I therefore desire a broad interpretation of my invention within the scope and spirit of the description herein, and of the claims appended hereinafter.

I claim: I

1. A return bend including a tube sheet into which a tube extends, a U member having a wing telescopically projecting into the tube sheet, and compression screws in screw threaded engagewent with the tube sheet, and in abutting con is tact with the sides and the wing of the U member to hold said members together.

2. Ina return bend of the class described, a tube sheet, a U member, said U member having projecting wing portions, said tube sheet having a screw threaded portion adjacent to the "pro-' jecting wing portions on said U member, and screw means normally in compression and in threaded engagement with said tube sheet, and tubes in abutting relation with said cover, said extending wing portions on the U member being of relatively large surface area to accommodate large cross section screw means whereby unit stresses in the screw means are reduced.

3. In a return bend of the class described, a tube sheet having a U member, said U member having projecting portions, said tube sheet having a screw threaded portion adjacent to the projecting portions on said U member, and screw means normally in compression inthreaded engagement with said tube sheet and in abutting relation with the projecting portions in said U member, said U member havin a partially cylindrical smooth bore surface serving as an abutmen-t for the compression screw means.

4. Av return bend including a tube sheet hav-" ing an outwardly projecting, portion partially cylindrical in cross section and being screw threaded, a U member fitting within said outwardly projecting portion, and having a'partially cylindrical smooth bore portion adjacent said screw an outwardly projecting portion partially cylindrical in cross section and being screw threaded, a U member fitting within said outwardly-projecting portion, and having a partially cylindrical smooth bore -.portion adjacent said screw threaded portion, and compression screws in screw threaded relation with the tube sheet and in abutting contact with the U member, said U member having a projecting wing portion in abutting contact with the bottom of the screw,

.said tube sheet having a tube therein, and a gasket between said U member and said tube.

6. A return bend having a tube sheet into which tubes extend, a U member to interconnect said tubes, a gasket between said U member and each of said tubes, said U member having a projecting wing portion extending above the gasket. substantially the thickness of the U member wall, said tube sheet extending above said wing portion, and a compression screw engaging the side of said U member and in abutting relation with said wing portion.

'7. A return bend of the class described, in-

- eluding a U member adapted to interconnect a plurality. of tubes, said U member having surfaces abutting said tubes, gasket means spaced trom the abutting surfaces to seal said tubes with respect to said U member, and means to secure said tubes to said U member including a tube sheet anchored to said tubes and detachable means to secure said tube sheet to said U member, said 1U member-having relatively low wing portions projecting from the sides thereof, the detach-able means abutting said wing portions substantially below the top of said U member.

8. A return bend to interconnect a plurality of tubular members, said return bend having wing portions projecting from the sides thereof closely adjacent to the tubular members, a tube sheet member engaging said tubular members and projecting above said wing portions and being provided with a screw thread surface less than 360 in extent, said return bend having a smooth bore opposite said screw threaded portion and securing means screw threaded in said tube sheet and held in said screw threaded position by abutment against the smooth bore of said return bend. v

GEORGE T. JACOCKS. 

